On Mon, Apr 13, 2009 at 5:18 PM, Richard Broersma
<richard.broersma@gmail.com> wrote:
>> Your PK is a composite of (entry, order)? Won't your foreign keys
>> elsewhere all break when you shift the order around?
>
> If there really are foreign keys, then an update will not be allowed
> to shift a primary key unless the foreign key is set with ON UPDATE
> CASCADE then the shifts will be cascaded to all references
> automatically.
Right. I'm still dusting off my SQL after a long period of corrosion. :)
The same applies, though, if you have external references to the PK;
for example, if you have a web interface where "/sense/10/3" refers to
entry 10, sense 3. If your senses are reordered by someone else, and
you operate on /10/3, you may suddenly find yourself viewing or
modifying (or deleting!) a different sense. This could even happen
within the same transaction, if you're not very careful with
locking...
--
Glenn Maynard